Background: Chromosomal abnormalities specifically associated with tumors of specific cell types often involve chromosomal regions in which reside genes encoding important differentiated functions of the involved cell type. We have previously demonstrated this fact for erythroleukemias in which translocations can often be found to involve the chromosomal bands on which are located the globin gene families. We have developed a long term research program involved in discovering the importance of the consistent involvement of the immunoglobulin gene encoding regions in the translocations observed in Burkitt lymphoma cells and other B-cell tumors. Over the past year, using this concept as a predictive and testable hypothesis, we have and are continuing to investigate the relationship of specific chromosomal abnormalities to certain tumors. Our focus at present is on diseases of the hematopoietic system. This research program rquires expertise in a number of distinct biological techniques. We have established this technical expertise which includes 1) our capability to grow and maintain a wide array of primary cells and cell lines 2) our facility in doing basic cytogenetic analyses, as well as the more involved procedure of chromosome in situ hybridization and, 3) our constantly updated ability to utilize the very newest of molecular biological techniques to clone, map, sequence and perform expression studies on DNA segments of interest. Mapping Studies: In collaboration with S. Korsmeyer, we have mapped to a specific band (18q21) on chromosome 18 a DNA segment that appears to define one constant region of the reciprocal exchange seen in patients with nodular lymphoma.